Combined RRC inactive resume, RRC RNA and NAS registration procedure

ABSTRACT

In accordance with an example embodiment of the present invention, a method comprising: sending, by a user equipment, a radio resource control (RRC) message, wherein the RRC message triggers transition of the user equipment from an RRC inactive state to an RRC connected state, wherein the RRC message is interpreted as a radio access network notification area (RNA) update; and receiving, by the user equipment, an RRC response message. The RRC message comprises a cause value indicating a combined RNA update with a non-access stratum (NAS) message.

TECHNICAL FIELD

This invention relates generally wireless communication and, particular,to user equipment starting a new resume procedure for uplink data.

BACKGROUND

This section is intended to provide a background or context to theinvention disclosed below. The description herein may include conceptsthat could be pursued, but are not necessarily ones that have beenpreviously conceived, implemented, or described. Therefore, unlessotherwise explicitly indicated herein, what is described in this sectionis not prior art to the description in this application and is notadmitted to be prior art by inclusion in this section.

3GPP Rel-15 5G specifications have introduced new state called “RRCInactive” or “RRC connected inactive”. In this state, the UE has usercontext established with the core NW as when he is in RRC connectedstate. However, from radio interface point of view the user is in “idle”mode in the sense that he is not continuously sending and receivingUL/DL data and thus not allocated all radio resources required forsending and receiving UL/DL data. When UE moves to new RNA and TA at thesame time, the UE needs to send both RAN notification area updates andcore network registrations when he leaves related areas.

While RRC inactive state is a new state defined in the current 3GPPspecification, this new state definition does not at the moment addresshow the coinciding messages are sent. If these updates are sentseparately even when their sending coincides timewise, radio resourcesare wasted and handling of the messages is more complex and prone toerrors. This also applies to closely enough timewise sending forperiodic updates. The need for combined update happens normally due to aUE move but it could happen also due to coinciding timer values. Timervalues can also be different for the two, but they could be set so thatevery Nth, e.g. every 10^(th), coincides.

The current invention moves beyond these techniques.

Acronyms or abbreviations that may be found in the specification and/orthe drawing figures are defined within the context of this disclosure oras follows below:

3GPP Third Generation Partnership Project

5G 5th Generation

ACK Acknowledgement

BS Base Station

DCI Downlink Control Information

DL Downlink

eMBB enhanced Mobile Broadband

eNB or eNodeB base station, evolved Node B

gNB NR/5G Node B

IE Information Element

IP Internet Protocol

IMT International Mobile Telecommunications (4, 4.5 or 5G)

LTE Long Term Evolution

LTE-A Long Term Evolution—Advanced

MCS Modulation and Coding Scheme

MBB Mobile Broadband

MME Mobility Management Entity

MSG Message

NACK Negative Acknowledgement

NCE Network Control Entity

NG Next Generation

NGAP NG Application Protocol

NG-RAN NG Radio Access Network

NR New Radio, NR Radio Access

NW Network

RA Resource Allocation

RAN Radio Access Network

RAR Random Access Response

RB Resource Block

Rel Release

RE Resource Element

RNA RAN notification area

RS Reference Signal

RRC Radio Resource Control

Rx Receive, Reception, or Receiver

TA Tracking Area

TS Technical Specification

Tx Transmit, Transmission, or Transmitter

UE User Equipment

UL Uplink

SUMMARY

Various aspects of examples of the invention are set out in the claims.

According to a first aspect of the present invention, a methodcomprising: sending, by a user equipment, a radio resource control (RRC)message, wherein the RRC message triggers transition of the userequipment from an RRC inactive state to an RRC connected state, whereinthe RRC message is interpreted as a radio access network notificationarea (RNA) update; and receiving, by the user equipment, an RRC responsemessage.

According to a second aspect of the present invention, an apparatuscomprising: at least one processor; and at least one memory includingcomputer program code, wherein the at least one memory and the computerprogram code are configured, with the at least one processor, to causethe apparatus to at least: send a radio resource control (RRC) message,wherein the RRC message triggers transition of the apparatus from an RRCinactive state to an RRC connected state, wherein the RRC message isinterpreted as a radio access network notification area (RNA) update;and receive an RRC response message.

According to a third aspect of the present invention, A non-transitorycomputer storage medium encoded with a computer program, the programcomprising instructions that when executed by one or more computerscause the one or more computers to perform operations comprising:sending, by a user equipment, a radio resource control (RRC) message,wherein the RRC message triggers transition of the user equipment froman RRC inactive state to an RRC connected state, wherein the RRC messageis interpreted as a radio access network notification area (RNA) update;and receiving, by the user equipment, an RRC response message.

According to a fourth aspect of the present invention, a methodcomprising: receiving, by a network node, a radio resource control (RRC)message from a user equipment, wherein the RRC message triggerstransition of the user equipment from an RRC inactive state to an RRCconnected state, wherein the RRC message is interpreted as a radioaccess network notification area (RNA) update; and sending, by thenetwork node, an RRC response message to the user equipment.

According to a fifth aspect of the present invention, an apparatuscomprising: at least one processor; and at least one memory includingcomputer program code, wherein the at least one memory and the computerprogram code are configured, with the at least one processor, to causethe apparatus to at least: receive a radio resource control (RRC)message from a user equipment, wherein the RRC message triggerstransition of the user equipment from an RRC inactive state to an RRCconnected state, wherein the RRC message is interpreted as a radioaccess network notification area (RNA) update; and send an RRC responsemessage to the user equipment.

According to a sixth aspect of the present invention, A non-transitorycomputer storage medium encoded with a computer program, the programcomprising instructions that when executed by one or more computerscause the one or more computers to perform operations comprising:receiving, by a network node, a radio resource control (RRC) messagefrom a user equipment, wherein the RRC message triggers transition ofthe user equipment from an RRC inactive state to an RRC connected state,wherein the RRC message is interpreted as a radio access networknotification area (RNA) update; and sending, by the network node, an RRCresponse message to the user equipment.

BRIEF DESCRIPTION OF THE DRAWINGS

In the attached Drawing Figures:

FIG. 1 is a block diagram of an exemplary system in which the exemplaryembodiments may be practiced;

FIG. 2 is a schematic of a UE triggered transition from RRC_INACTIVE toRRC_CONNECTED;

FIG. 3 is a schematic of an RNA Update;

FIG. 4 is a schematic of Core NW Registration;

FIG. 5 through FIG. 16 are schematics of exemplary embodiments of anapparatus of the present invention;

FIG. 17 is a block diagram of an example of 5G non-roaming architecture.

DETAILED DESCRIPTION OF THE DRAWINGS

The word “exemplary” is used herein to mean “serving as an example,instance, or illustration.” Any embodiment described herein as“exemplary” is not necessarily to be construed as preferred oradvantageous over other embodiments. All of the embodiments described inthis Detailed Description are exemplary embodiments provided to enablepersons skilled in the art to make or use the invention and not to limitthe scope of the invention which is defined by the claims.

As described in more detail below, an RNA update may coincide with coreNW registration update or other similar procedures such as “N2Notification procedure/AMF requested NG-RAN location updating”. Tooptimize such coinciding procedures, this invention the following oneprocedure:

Initiate RRC Resume procedure.

Combine RRC Resume procedure with RRC RNA Update and NAS Registration.Interpret RRCResumeRequest as RNA update. The request message cancontain a cause value explicitly indicating combined RNA update and acore NW level NAS registration procedure. The RRCResumeRequest cancontain RAN update related parameters. Include NAS Registration (orother similar) message in RRCResumeRequest and it is then furtherprovided over N2 to AMF with NGAP Uplink NAS Transport (or other NGAP)message. (Note that these message names are examples of message namesand that the current invention should not be limited only to thesemessage names if later some other names will be defined.)

RRCResume/Release could contain additional RNA information to be used bythe UE in the new RNA and/or Tracking Area/Registration area from thecore NW. RRCResume/Release may contain NAS level acknowledgement to theNAS registration request (or other NAS message), e.g. such NAS levelmessage or related parameter(s) in RRC message. Nonetheless, thisparagraph and the one above are not describing all the message exchangepossibilities.

Before turning to how an exemplary embodiment would function, FIG. 1 ispresented showing a block diagram of one possible and non-limitingexemplary system in which the exemplary embodiments may be practiced. InFIG. 1, a user equipment (UE) 110 is in wireless communication with awireless network 100. A UE is a wireless, typically mobile device thatcan access a wireless network. The UE 110 includes one or moreprocessors 120, one or more memories 125, and one or more transceivers130 interconnected through one or more buses 127. Each of the one ormore transceivers 130 includes a receiver, Rx, 132 and a transmitter,Tx, 133. The one or more buses 127 may be address, data, or controlbuses, and may include any interconnection mechanism, such as a seriesof lines on a motherboard or integrated circuit, fiber optics or otheroptical communication equipment, and the like. The one or moretransceivers 130 are connected to one or more antennas 128. The one ormore memories 125 include computer program code 123. Note that the YYYmodule allows functionality for the usage of control resources for datatransmission where any method or examples of such embodiments discussedherein can be practiced. The UE 110 includes a YYY module 140,comprising one of or both parts 140-1 and/or 140-2, which may beimplemented in a number of ways. The YYY module 140 may be implementedin hardware as YYY module 140-1, such as being implemented as part ofthe one or more processors 120. The YYY module 140-1 may be implementedalso as an integrated circuit or through other hardware such as aprogrammable gate array. In another example, the YYY module 140 may beimplemented as YYY module 140-2, which is implemented as computerprogram code 123 and is executed by the one or more processors 120. Forinstance, the one or more memories 125 and the computer program code 123may be configured to, with the one or more processors 120, cause theuser equipment 110 to perform one or more of the operations as describedherein. The UE 110 communicates with base station 170 via a wirelesslink 111.

The base station 170 (which in the shown embodiment is a Radio AccessNode (RAN), a gNB, NR/5G Node B, or possibly an evolved NodeB for LTEconnected to 5GC, long term evolution, but could be any similar accesspoint to a wireless network) that provides access by wireless devicessuch as the UE 110 to the wireless network 100. The base station 170includes one or more processors 152, one or more memories 155, one ormore network interfaces (N/W I/F(s)) 161, and one or more transceivers160 interconnected through one or more buses 157. Each of the one ormore transceivers 160 includes a receiver, Rx, 162 and a transmitter,Tx, 163. The one or more transceivers 160 are connected to one or moreantennas 158. The one or more memories 155 include computer program code153. Note that the ZZZ module allows functionality for the usage ofcontrol resources for data transmission where any method or examples ofsuch embodiments discussed herein can be practiced. The base station 170includes a ZZZ module 150, comprising one of or both parts 150-1 and/or150-2, which may be implemented in a number of ways. The ZZZ module 150may be implemented in hardware as ZZZ module 150-1, such as beingimplemented as part of the one or more processors 152. The ZZZ module150-1 may be implemented also as an integrated circuit or through otherhardware such as a programmable gate array. In another example, the ZZZmodule 150 may be implemented as ZZZ module 150-2, which is implementedas computer program code 153 and is executed by the one or moreprocessors 152. For instance, the one or more memories 155 and thecomputer program code 153 are configured to, with the one or moreprocessors 152, cause the base station 170 to perform one or more of theoperations as described herein. The one or more network interfaces 161communicate over a network such as via the links 176 and 131. Two ormore base stations 170 communicate using link 178, while the basestation can communicate with other entities via link 176, where bothlink 176, sand 178 may be wired or wireless or both and may implement,e.g., an Xn interface.

The one or more buses 157 may be address, data, or control buses, andmay include any interconnection mechanism, such as a series of lines ona motherboard or integrated circuit, fiber optics or other opticalcommunication equipment, wireless channels, and the like. For example,the one or more transceivers 160 may be implemented as a remote radiohead (RRH) 195, with the other elements of the base station 170 beingphysically in a different location from the RRH, and the one or morebuses 157 could be implemented in part as fiber optic cable to connectthe other elements of the base station 170 to the RRH 195.

It is noted that description herein indicates that “cells” performfunctions, but it should be clear that the base station that forms thecell would perform the functions. The cell makes up part of a basestation. That is, there can be multiple cells per base station. Forinstance, there could be three cells for a single base station carrierfrequency and associated bandwidth, each cell covering one-third of a360-degree area so that the single base station's coverage area coversan approximate oval or circle. Furthermore, each cell can correspond toa single carrier and a base station may use multiple carriers. So ifthere are three 120-degree cells per carrier and two carriers, then thebase station has a total of 6 cells.

The base station 170 is coupled via a link 131 to the some other networknode 190. The link 131 may be implemented as a type of interface that isnot necessarily wireless. The other network node 190 includes one ormore processors 175, one or more memories 171, and one or more networkinterfaces (N/W I/F(s)) 180, interconnected through one or more buses185. The one or more memories 171 include computer program code 173. Theone or more memories 171 and the computer program code 173 areconfigured to, with the one or more processors 175, cause the NCE 190 toperform one or more operations.

Moreover, the Radio Access Network (RAN) also has “logical” elements,namely, a Central Unit (CU) and a Distributed Unit (DU). The CU is alogical node which may include the functions (i.e., gNB functions) suchas transfer of user data, mobility control, radio access networksharing, positioning, session management, etc., except those functionsallocated exclusively to the DU. The CU may control the operation of DUsover a front-haul (F1) interface. The CU may also be known asBBU/REC/RCC/C-RAN/V-RAN. The DU is a logical node which may include asubset of the functions (i.e., gNB functions), depending on thefunctional split option. The operation of the DU may be controlled bythe CU. A Distributed Unit (DU) may also be known with other names likeRRH/RRU/RE/RU. The DU may also contain intra-DU interfaces, e.g. E1interface between its user and control plane functions.

The wireless network 100 may implement network virtualization, which isthe process of combining hardware and software network resources andnetwork functionality into a single, software-based administrativeentity, a virtual network. Network virtualization involves platformvirtualization, often combined with resource virtualization. Networkvirtualization is categorized as either external, combining manynetworks, or parts of networks, into a virtual unit, or internal,providing network-like functionality to software containers on a singlesystem. Note that the virtualized entities that result from the networkvirtualization are still implemented, at some level, using hardware suchas processors 152 or 175 and memories 155 and 171, and also suchvirtualized entities create technical effects. With the cloud, the RANand core could be also fully or partially in same cloud element(s). Alsoan N2 and/or other interfaces could be substituted with data repositoryetc.

The computer readable memories 125, 155 and 171 may be of any typesuitable to the local technical environment and may be implemented usingany suitable data storage technology, such as semiconductor based memorydevices, flash memory, magnetic memory devices and systems, opticalmemory devices and systems, fixed memory and removable memory. Thecomputer readable memories 125, 155, and 171 may be means for performingstorage functions. The processors 120, 152, and 175 may be of any typesuitable to the local technical environment, and may include one or moreof general purpose computers, special purpose computers,microprocessors, digital signal processors (DSPs) and processors basedon a multi-core processor architecture, as non-limiting examples. Theprocessors 120, 152, and 175 may be means for performing functions, suchas controlling the UE 710, base station 770, and other functions asdescribed herein.

In general, the various embodiments of the user equipment 110 caninclude, but are not limited to, cellular telephones such as cellularphones, smart devices, personal digital assistants (PDAs) havingwireless communication capabilities, portable computers having wirelesscommunication capabilities, image capture devices such as digitalcameras having wireless communication capabilities, gaming deviceshaving wireless communication capabilities, music storage and playbackappliances having wireless communication capabilities, Internetappliances permitting wireless Internet access and browsing, tabletswith wireless communication capabilities, as well as portable units orterminals that incorporate combinations of such functions. In addition,various embodiments of the user equipment include machines,communicators and categories of equipment, which are not primarily ornot at all in use by human interaction.

Embodiments herein may be implemented in software (executed by one ormore processors), hardware (e.g., an application specific integratedcircuit), or a combination of software and hardware. For example, in anembodiment, the software (e.g., application logic, an instruction set)is maintained on any one of various conventional computer-readablemedia. In the context of this document, a “computer-readable medium” maybe any media or means that can contain, store, communicate, propagate ortransport the instructions for use by or in connection with aninstruction execution system, apparatus, or device, such as a computer,with one example of a computer described and depicted, as in FIG. 1 forexample. A computer-readable medium may comprise a computer-readablestorage medium (e.g., memories 125, 155, 171 or other device) that maybe any media or means that can contain or store the instructions for useby or in connection with an instruction execution system, apparatus, ordevice, such as a computer.

The current 3GPP Release 8 based architecture in LTE networks is fullydistributed in the radio and fully centralized in the core network. Thelow latency requires bringing the content close to the radio which leadsto local break out and multi-access edge computing (MEC). 5G (andevolved LTE connected to 5G core) may use edge cloud and local cloudarchitecture. Edge computing covers a wide range of technologies such aswireless sensor networks, mobile data acquisition, mobile signatureanalysis, cooperative distributed peer-to-peer ad hoc networking andprocessing also classifiable as local cloud/fog computing and grid/meshcomputing, dew computing, mobile edge computing, cloudlet, distributeddata storage and retrieval, autonomic self-healing networks, remotecloud services and augmented reality. In radio communications, usingedge cloud may mean node operations to be carried out, at least partly,in a server, host or node operationally coupled to a remote radio heador base station comprising radio parts. It is also possible that nodeoperations will be distributed among a plurality of servers, nodes orhosts. It should also be understood that the distribution of laborbetween core network operations and base station operations may differfrom that of the LTE or even be non-existent. Some other technologyadvancements probably to be used are Software-Defined Networking (SDN),Big Data, and all-IP, which may change the way networks are beingconstructed and managed.

One possible manner to carry out embodiments described herein is with anedge cloud using a distributed computing system. An exemplary embodimentcomprises a radio node connected to a server. Exemplary embodimentsimplementing the system allow the edge cloud server and the radio nodeas stand-alone apparatuses communicating with each other via a radiopath or via a wired connection or they may be located in a same entitycommunicating via a wired connection.

Regarding RNA and core location updates in RRC Inactive state, the corenetwork provides 5G RAN with RRC Inactive assistance information. Theinformation contains among other things the UE's Registration area andPeriodic registration area timer. The 5G RAN assigns the UE with RANnotification area (RNA) which is (meaning it contains the cells of or itcan also include RAN area list instead of cell list) the registrationarea or subset of it. The RAN uses the RNA to page the UE in it when theUE is in RRC Inactive state.

When UE is in RRC inactive state, it shall make RNA update either whenit leaves the RNA area, such that it enters a cell that is not part ofthe RNA assigned for it (or when UE moves out of defined RAN areas,which is similar, rather than in core network registration area updateprocedure), or upon expiry of the periodic RAN Notification Area Updatetimer.

When UE is registered in core NW, it shall make registration requeststowards core network (AMF) upon changing to new (cell in) Tracking Areaoutside the UE's Registration area or upon expiry of periodicregistration update timer (when UE is requested to make periodicregistrations (location updates).

Additionally, for N2 Notification procedure/AMF requested NG-RANlocation reporting, to support the UE's location information morestringently (e.g. cell information for emergency calls), per requestonce, periodically, or with regards to “Area of Interest”, the RAN mayreport UE's location (cell, TAI) and other needed UE information to coreNW (AMF) as requested.

FIG. 2 shows UE triggered transition from RRC_INACTIVE to RRC_CONNECTEDwhere: (1) The UE resumes from RRC_INACTIVE, providing the I-RNTI,allocated by the last serving base station; (2) The base station, ifable to resolve the base station identity contained in the I-RNTI,requests the last serving base station to provide UE Context data; (3)The last serving base station provides UE context data; (4) The basestation completes the resumption of the RRC connection; (5) If loss ofDL user data buffered in the last serving base station shall beprevented, the base station provides forwarding addresses; (6/7) Thebase station performs path switch; and (8) The base station triggers therelease of the UE resources at the last serving base station.

FIG. 3 shows an RNA Update where: (1) The UE resumes from RRC_INACTIVE,providing the I-RNTI allocated by the last serving base station andappropriate cause value, e.g., RAN notification area update; (2) Thebase station, if able to resolve the base station identity contained inthe I-RNTI, requests the last serving base station to provide UEContext; (3) The last serving base station provides UE context; (4) Thebase station may move the UE to RRC_CONNECTED, or send the UE back toRRC_INACTIVE state or send the UE to RRC_IDLE. (Note a problem incurrent 3GPP 38.331 is that RAN will move the UE directly back to RRCinactive and then the UE would need to do new request for a registrationarea update. Without changing this, the network does not have any reasonto move the UE back to RRC connected in RNA update procedure.) If the UEis sent to RRC_IDLE, the following steps are not needed; (5) If loss ofDL user data buffered in the last serving base station shall beprevented, the base station provides forwarding addresses; (6/7). Thebase station performs path switch; and (8) The base station triggers therelease of the UE resources at the last serving base station.

Regarding core NW registration, FIG. 4 shows the complete UERegistration procedure. The complete registration flow is not neededwith location update for a UE that is already registered. However. FIG.4 does not show AMF re-allocation but it may be carried as part of theregistration if the AMF does not serve the UE's new location (Trackingarea).

A problem solved by the current invention is that, when a UE moves tonew RNA and new TA, it needs to perform both RNA update and registrationupdate. Additionally, the same problem could also happen if the UE hasthe same timer value for RNA and TA/registration area update.

Currently 3GPP does not clearly specify how this can be done. If a UEwould make first registration update it would lead to loss of oldinactive UE context as a new base station would not be able to identifyand connect the request. If that UE first makes an RNA update, thenafter that a new resume for UL data. However, this is very suboptimalbecause in the RNA update procedure the new base station only checksthat the UE context is valid in the previous base station but does notmove the UE context to the new base station. After an RNA update, the UEneeds to perform a new resume for UL data and only this procedure movesthe UE context from the previous base station to the new base stationand moves the UE RRC connected, where the UE can initiate registrationupdate.

In LTE, a UE performs TAU with uplink information transfer message whenUE is in RRC connected mode or, if the UE comes from an RRC idle, thenit combines it with an RRC Connection Setup Complete message

In the present invention, the UE performs the RNA update with RRC resumeand combines registration to that message. The network identifies thecase and makes context move and after that registration update.

Another issue is that if UE context fetch is not successful from sourcebase station, then the network shall move the UE to RRC connected modeand perform the registration and thereafter moves the UE RRC idle.

The RNA update (shown in FIG. 3 and discussed above) may coincide withcore NW registration update (see FIG. 4, also discussed above) or othersimilar procedures such as “N2 Notification procedure/AMF requestedNG-RAN location updating”. To optimize such coinciding procedures,current invention puts these together with one procedure as follows:

First, initiate RRC Resume procedure as described FIG. 3.

Second, combine RRC Resume procedure with RRC RNA Update and NASRegistration. Interpret the first message in RRC Resume procedure(RRCResumeRequest) as RNA update, the request message can contain causevalue explicitly indicating combined RNA update and core NW level NASregistration procedure. The RRCResumeRequest can contain RAN updaterelated parameters. Include NAS Registration (or other similar) messagein RRCResumeRequest and further providing it over N2 to AMF with NGAPUplink NAS Transport (or other NGAP) message.

Third, alternatively interpret the third message (RRCResumeComplete) inthe RRC resume procedure as combined RNA update, the complete messagecan contain cause value indicating RNA update and core NW level NASregistration request.

Lastly, RRCResume/Release could contain additional RNA information to beused by the UE in the new RNA and/or Tracking Area/Registration areafrom the core NW.

Note that the UE context can be retrieved from last serving base stationand Path Switch procedure towards core NW carried out, if the lastserving base station is not the new/current base station

Additionally, the core NW could provide back e.g. answer message whichcould be conveyed in SRB or embedded in RRCResume/Release message whichis provided from RAN towards UE as reply.

Moreover, the RNA and registration location updates may be due toentering new cell which is not part of current RNA and/or TA, or due toperiodic RNA/registration update.

The RNA update (shown in FIG. 3 and discussed above) may coincide withcore NW registration update (see FIG. 4, also discussed above) or othersimilar procedures such as “N2 Notification procedure/AMF requestedNG-RAN location updating”. To optimize such coinciding procedures,current invention puts these together with one procedure as follows:

First, initiate RRC Resume procedure as described FIG. 3.

Second, combine RRC Resume procedure with RRC RNA Update and NASRegistration. Interpret RRCResumeRequest as RNA update, the requestmessage can contain cause value explicitly indicating combined RNAupdate and core NW level NAS registration procedure. TheRRCResumeRequest can contain RAN update related parameters. Include NASRegistration (or other similar) message in RRCResumeRequest and furtherproviding it over N2 to AMF with NGAP Uplink NAS Transport (or otherNGAP) message.

Lastly, RRCResume/Release could contain additional RNA information to beused by the UE in the new RNA and/or Tracking Area/Registration areafrom the core NW.

Note that the UE context can be retrieved from last serving base stationand Path Switch procedure towards core NW carried out, if the lastserving base station is not the new/current base station

Additionally, the core NW could provide back e.g. answer message whichcould be conveyed in SRB or embedded in RRCResume/Release message whichis provided from RAN towards UE as reply.

Moreover, the RNA and registration location updates may be due toentering new cell which is not part of current RNA and/or TA, or due toperiodic RNA/registration update.

FIG. 5, FIG. 6, and FIG. 7 present signaling flows for the variouscases. For simplicity, the cases describe the situations in which theRNA and TAI/RA (Registration area) changes. With periodic RNA & RAupdate, the updating can happen without RNA/RA change. The flows areequal in such case apart from some minor differences in proceduredetails.

Additional flows which are not explicitly included are the following: DUchange without CU change within base station; AMF change, if AMF ischanged, UE information is retrieved from previous AMF, UDM is updatedwith UE's new location, etc. (for more information see 3GPP TS 23.502);and UPF change (again, please 3GPP TS 23.502).

Otherwise the flows show RA update but messages between base station CUand DU are mostly omitted for simplicity. Also for the sake ofsimplicity, all generic functionality related to the procedures, e.g.all messages may not be included in the figures.

In FIG. 5, the base station is changed, UE context retrieved from thelast serving base station. As such, the UE's RNA & TA changes withoutRAN DU, RAN CU, and AMF changing.

RRCRequest may contain specific cause code value indicting that this iscombined RNA & registration update. RRCResume (Release) may containinformation on acknowledgement on the RNA change as well as additionalinformation related to the new RNA. In addition, UE may retrieve suchinfo via SIB s etc. The NAS registration update message is included inRRC message as “DedicatedNASlnfo” IE. This is most optimal from airinterface signaling point of view. In addition, it is less error proneas the NAS message is not lost if target the base station does notrecognize it, for instance, if the UE context is not successfullyretrieved from the last serving base station. NAS level acknowledgementis returned within RRCConnectionResume or as independent RRC DownlinkTransport, or in other relevant message.

In step 1, the base station records a new RNA for the UE. Informationabout NAS level registration is indicated with a separate NAS messageincluded in the RRC message, as an IE (or several IEs) in an RRCmessage, or deduced from the fact that RNA (cell) changes, for instance,if RNA area equals Registration area. NAS Registration may be sent tothe AMF as its own message using existing NGAP context with NGAP UL NASTransport or combined with another NGAP message such as Path SwitchRequest.

In step 4, the RNA and/or RA change is acknowledged as IE(s) with theRRC message and/or NAS message. Additional related information can alsobe provided to the UE.

In step 6, new TAI/RA (cell) is recorded if not done previously in AMFand other core NW elements as needed (including HSS, PCRC/PCF,applications etc.). The new TAI/RA is indicated as separate NAS messageor as one (or more) IE(s) within Path Switch Request. Possible relatedadditional information may be returned to UE in NGAP and RRC acknowledgemessage or as separate NGAP and RRC messages, with incorporated NASmessage or as IE(s) in NGAP and RRC messages.

Note that the order of the messages may vary, for instance, step 4 couldbe after step 7.

In FIG. 6, the base station is not changed. As such, the UE's RNA & TAchanges without RAN DU, RAN CU and AMF change. With the same basestation, the CU, for example, is also supporting the new NRA & TA asshown in FIG. 5.

If UE is moved to RRC idle, then RRCResumeComplete is not sent. If UE ismoved to RRC Connected mode then the RRCResumeComplete is sent. Sendingof RRC NAS DL Transport depends on whether it is needed to send the NASlevel ack, e.g. if sent already in RRResume/Release, then could beomitted. NAS “RA Update” may be sent in RRCResumeRequest and/or inRRCResumeComplete message(s). “RA update ack” may be sent in eitherRRCresume/release and/or in “RRCNASDLTransport” message(s).

FIG. 7 shows the error case with a base station change, such that the UEcontext fetch from last serving base station fails. As such, a new RRCconnection and NGAP context to core NW is established. Here the UE's RNA& TA changes without RAN DU, RAN CU, and AMF changing.

In step 4, as the UE context is not successfully retrieved from lastserving base station, the base station needs to setup the RRC Connectionwith RRCConnectionSetup. In step 6, the AMF (and other needed core NWelements and functions) records the UE's new RA, establishes UE contexttowards new base station, and removes context towards last serving basestation, if it still exists. See FIG. 6 for additional notes and actionsrelated to RNA/RA.

FIG. 8 through FIG. 13 give more detailed flows. The “NAS message “inNGAP or RRC can be NAS registration request, NAS registration accept orNAS registration complete (las is conditional message) PDU, or anotherNAS message, or NAS like information included as information elements inRRC and/or NGAP messages replacing or providing additional informationto the NAS message.

Case 1: no gNB change and UE context found in the gNB: existing NGAP UEcontext between RAN and core NW can be used, e.g. NGAP Uplink NASTransport including the NAS registration.

Case 2: gNB change and so UE context need to be fetched from previousgNB over Xn interface, here are 3 different cases w.r.t. to NGAP UEcontext:

(a) NAS message is sent to core NW with establishing new NGAP UE contextbetween RAN and core NW with S-TMSI or other UE identity received in theRRC (resume request) message. This is can be done before the UE contextis fetched from the previous gNB, e.g. by using NGAP Initial UE messageand Initial context setup/Downlink NAS Transport procedure, orsimultaneously with that fetching. The new UE NGAP context can be: (i)immediately removed after “NAS registration accept” (or other NASmessage), and e.g. followed by NGAP Path Switch procedure; or (ii) thenew NGAP context can be continued and used for Path Switch;

(b) The UE context is fetched first from the previous gNB and new NGAPcontext created between new gNB and core NW for the UE, e.g. with NGAPPath Switch procedure (and the old one removed). E.g. the NASregistration and registration accept messages are conveyed in NGAP PathSwitch request and acknowledge messages, respectively, or as separateNGAP Uplink and Downlink NAS Transport messages using the alreadyestablished NGAP UE context, respectively.

(c) NAS message is sent to core NW with establishing new NGAP UE contextbetween RAN and core NW with S-TMSI or other UE identity received in theRRC (resume request) message by e.g. using NGAP Initial UE message andInitial context setup procedure. This is can be done even if UE contextfetching from old gNB is not done or if the new gNB does not have UEcontext.

Case 3: If UE context is not found and RRC connection setup needs to besent to the UE as response to the RRC resume req, then new UE NGAP setupto core NW needs to be established for the NAS signaling, e.g. with NGAPInitial UE message and Initial context setup procedure

To overcome these issues, the present invention combines the RNA updateand core NW registration with RRC Resume procedure. FIG. 8 through FIG.13 detail the particular message flows with the combined RNA and NASregistration.

NAS registration request (and/or corresponding IEs) can be in an uplinkRRC message, being conveyed as part of or in conjunction with theprocedures to update the “RAN update” and carry out related actions, as“DedicatedInfoNAS” or other similar IE, examples: RRC Connection ResumeRequest; RRC Connection Resume Complete; RRC Connection Setup; RRC ULInformation Transfer.

After NAS Registration request, NAS registration accept (and/orcorresponding IEs) is in any subsequent downlink RRC message, followingRRC message that conveyed the uplink NAS registration, as“DedicatedInfoNAS” or other similar IE, examples: RRC Connection Resume;RRC Connection Release; RRC Connection Setup Complete; RRC DLInformation Transfer.

After NAS Registration Accept, NAS registration complete (and/orcorresponding IEs) may follow as third step and be in an uplink RRCmessage, being conveyed as part of or in conjunction with the proceduresto update the “RAN update” and carry out related actions, as“DedicatedInfoNAS” or other similar IE, examples: RRC Connection ResumeComplete; RRC Connection Setup; RRC UL Information Transfer.

FIG. 8 shows the flows where the gNB is not changed with combined RNAand NAS registration.

FIG. 9 shows the flows where the gNB is not changed with combined RNAand NAS registration.

FIG. 10 shows the message flows were the gNB is changed with combinedRNA and NAS registration.

FIG. 11 shows the message flows where the gNB is changed with combinedRNA and NAS registration; UE context not found.

Another option: note, especially in these options, the NAS messages canbe sent as part of other needed RRC messages in UL and DL or as RRCUL/DL Information Transfer.

FIG. 12 shows the message flows where the gNB is not changed, withcombined RNA and NAS registration.

FIG. 13 shows the message flows where gNB is not changed, with combinedRNA and NAS registration.

FIG. 14 shows the message flows where the gNB is not changed, withcombined RNA and NAS registration. May be omitted: NAS registrationcomplete in RRC Resume Complete and corresponding F1 message; NGAP ULNAS Transport with NAS “registration complete”.

FIG. 15 shows the message flows were the gNB is changed with combinedRNA and NAS registration.

FIG. 16 shows the message flows were the gNB is not changed withcombined RNA and NAS registration and shows that there are differentoptions for combining the NAS messages with RRC messages

Exemplary methods can be found in each on the message flow diagrams. Thevarious processors, memories, and computer program codes, especiallythose found in the YYY modules and ZZZ modules described hereinabovewould execute the method in the particular device. An apparatuscomprising at least one processor and at least one memory includingcomputer program code, wherein the at least one memory and the computercode are configured, with the at least one processor, would cause theapparatus to at least perform each of the steps of all the exemplarymethods discusses herein. Moreover, a computer program product embodiedon a non-transitory computer-readable medium in which a computer programis stored that, when being executed by a computer, could also beconfigured to provide instructions to control or carry out each andevery step of each and every exemplary method discussed herein.

Furthermore, an apparatus with means for carrying out each and everystep of each and every exempla method would be an aspect of the presentinvention as would a computer program with code for carrying out eachand every step of each and every exemplary method would be an aspect ofthe present invention.

Although various aspects of the invention are set out in herein, otheraspects of the invention comprise other combinations of features fromthe described embodiments and/or the dependent with the features of themanifestations, and not solely the combinations explicitly set out inthe claims.

Below are presented several manifestations of the present inventionwhere different signaling is shown for each depending on the scenario.The first manifestation shows an exemplary method where there is an RNAchange with immediate inactive after context fetch and delivery of NASmessage to the core network. This procedure, denoted as manifestation 1,like manifestations 2, 3 ,4, and 5, which follow, may also be used ingNB internal in a case where the gNB is split to several RNAs:

1. A method comprising:

-   -   in response to changing base stations, receiving by BS2 from a        UE served by BS1 an RCCResumeRequest,        -   wherein the RRCResumeRequest comprises:            -   parameters related to the RAN update            -   a cause value indicating a combined RNA update,            -   a NAS Registration message, and        -   wherein the RCCResumeRequest is interpreted as an RNA            update;    -   sending by BS2 a Retrieve UE Context Request to BS1;    -   obtaining by BS2 from BS1 a UE Context Response; and    -   transmitting by BS2 a Release to the UE.

The second manifestation is for an RNA with RRC connection. In thiscase, it is expected that RRC connection needs to be maintained for awhile, for instance, for acknowledgement from the core network:

2. A method comprising:

-   -   in response to changing base stations, receiving by BS2 from a        UE served by BS1an RCCResumeRequest,        -   wherein the RRCResumeRequest comprises:            -   parameters related to the RAN update            -   a cause value indicating a combined RNA update,            -   a NAS Registration message, and        -   wherein the RCCResumeRequest is interpreted as an RNA            update;    -   sending by BS2 a Retrieve UE Context Request to BS1;    -   obtaining by BS2 from BS1 a UE Context Response;    -   transmitting by BS2 an RCCResume to the UE;    -   receiving RRCComplete from the UE;    -   transmitting by BS2 a Release to the UE.

This third manifestation is for periodic RNA. This is similar to thefirst and second manifestations shown above and could actually havesimilar to those types of manifestations short and longer formats:

3. A method comprising:

-   -   in response to a periodical RNA/RA update, receiving by a BS in        the RNA from a UE served by BS1 an RCCResumeRequest,        -   wherein the RRCResumeRequest comprises:            -   parameters related to the RAN periodic update            -   a cause value indicating a combined RNA periodic update,            -   a NAS Registration message, and        -   wherein the RCCResumeRequest is interpreted as an RNA            update;    -   in case BS1/=BS2 sending by BS2 a Retrieve UE Context Request to        BS1;    -   obtaining by BS2 from BS1 a UE Context Response; and    -   transmitting by BS2 an RCCResume/Release to the UE.

This next manifestation, the fourth one, is in regard to RNA with RRCconnection, namely, an NAS message in RRC resume complete. In thismanifestations, a NAS message is delivered in the second UE message; sothe UE is first moved to RRC connected and then the NAS signaling startsafter that:

4. A method comprising:

-   -   in response to changing base stations, receiving by BS2 from a        UE served by BS1 an RCCResumeRequest,        -   wherein the RRCResumeRequest comprises:            -   parameters related to the RAN update            -   a cause value indicating a combined RNA update,        -   wherein the RCCResumeRequest is interpreted as an RNA            update;    -   sending by BS2 a Retrieve UE Context Request to BS1;    -   obtaining by BS2 from BS1 a UE Context Response; and    -   transmitting by BS2 an RCCResume to the UE.    -   receiving RRCResumeComplete from the UE with a NAS Registration        message transmitting by BS2 a Release to the UE.

In this fifth manifestation, any type of NAS message in RRC resumecomplete, for instance, UL NAS transport message, is shown, which couldbe combined with the above manifestations:

5. A method comprising:

-   -   in response to changing base stations, receiving by BS2 from a        UE served by BS1 an RCCResumeRequest,        -   wherein the RRCResumeRequest comprises:        -   parameters related to the RAN update        -   a cause value indicating a combined RNA update,        -   wherein the RCCResumeRequest is interpreted as an RNA            update;    -   sending by BS2 a Retrieve UE Context Request to BS1;    -   obtaining by BS2 from BS1 a UE Context Response; and    -   transmitting by BS2 an RCCResume to the UE.    -   receiving RRCResumeComplete from the UE    -   receiving UL NAS transport message from the UE    -   transmitting by BS2 a Release to the UE.

In this sixth manifestation, the messaging between the UE and BS2 is asfollows, which could be combined with the above manifestations:

6. A method comprising:

-   -   wherein the RRCResumeRequest comprises:    -   a cause value indicating e.g. “mo originated signaling”,    -   wherein the RRCResumeComplete comprises:        -   parameters related to the RAN update and/or        -   a cause value indicating a RNA update,        -   NAS Registration Request,        -   wherein the RCCResumeComplete is interpreted as an RNA            update;    -   sending by BS2 to AMF the NAS registration request in NGAP UL        NAS Transport message    -   obtaining by BS2 the NAS registration accept in NGAP DL NAS        Transport; and    -   transmitting by BS2 an RRC DL Information Transfer to the UE;        and possibly    -   obtaining by BS2 from UE RRC UL Information Transfer message or        other RRC message with NAS registration complete message from UE        in; and    -   transmitting by BS2 to AMF NGAP UL NAS Transport or other NGAP        message with NAS registration complete message.

In this seventh manifestation, the messaging between the UE and BS2 isas follows, which could be combined with the above manifestations:

7. A method comprising:

-   -   wherein the RRCResumeRequest comprises:    -   a cause value indicating e.g. “mo originated signaling”,    -   wherein the RRCResumeComplete comprises:        -   parameters related to the RAN update and/or        -   a cause value indicating a RNA update,        -   NAS Registration Request,        -   wherein the RCCResumeComplete is interpreted as an RNA            update;    -   sending by BS2 a Retrieve UE Context Request to BS1;    -   obtaining by BS2 from BS1 a UE Context Response; and    -   sending by BS2 to AMF the NAS registration request in NGAP Path        Switch request or other NGAP message    -   obtaining by BS2 the NAS registration accept in NGAP Path Switch        request response or in other NGAP message; and    -   transmitting by BS2 an RRC DL Information Transfer containing        the NAS registration accept to the UE; and possibly    -   obtaining by BS2 from UE RRC UL Information Transfer message or        other RRC message with NAS registration complete message from UE        in; and    -   transmitting by BS2 to AMF NGAP UL NAS Transport or other NGAP        message with NAS registration complete message.

In this eighth manifestation, the messaging between the UE and BS2 is asfollows, which could be combined with the above manifestations:

8. A method comprising:

-   -   wherein the RRCResumeRequest comprises:        -   a cause value indicating e.g. “mo originated signaling”,        -   wherein the BS2 sends XNAP Retrieve UE context request to            BS1, and        -   wherein the BS1 replies to BS2 with XNAP Retrieve UE context            rejection with “UE context not found”, and    -   wherein BS2 sends RRC Connection Setup to the UE, and        -   UE responds to BS2 with RRC Connection Setup Complete            comprises:            -   parameters related to the RAN update and/or            -   a cause value indicating a RNA update, and            -   NAS Registration request,        -   wherein BS2 sends to AMF NGAP Initial UE message comprises            -   NAS Registration Request            -   wherein the RRC Connection Setup Complete is interpreted                as an RNA update;        -   sending by AMF a NGAP Initial UE context Setup or NGAP DL            NAS Transport message with NAS Registration Accept to BS2;            and        -   sending by BS2 RRC DL Information Transfer with NAS            Registration accept to UE, and possibly        -   obtaining by BS2 from UE RRC UL Information Transfer message            or other RRC message with NAS registration complete message            from UE in; and        -   transmitting by BS2 to AMF NGAP UL NAS Transport or other            NGAP message with NAS registration complete message.

The above manifestations may contain “RNA update accept” with possiblyrelated information as separate parameter(s) or information indicatingfrom BS2 to UE that the update is accepted.

BS2, UE, and core network AMF typically record the RNA update andRegistration update and carry out related actions such as saving theinformation, setting supervision timer(s), etc. these are alreadyexplained in current specifications and not repeated here. Alsodifferent implementations may have additional functionality or omit orreplace some actions.

The descriptions focus on the functionality between a) the BS and UE, b)BS2 and core network (AMF), c) BS1 and BS2 (when applicable) and d) theNAS signaling between core NW AMF and UE (via BS2), and to some extentfunctionality by UE, BS1, BS2 and core NW AMF. All the internal aspectsof entities such as BS2 (or BS1) or core network are not explained, e.g.within BS2 there can be many internal interfaces, e.g. F1, E1, and manyothers. Those are not important from the invention perspective andmostly not described. Some possible example behavior of F1 interface isdepicted but message names and functionality can be different as therecan be many variants of F1 interface. Also some existing well knownfunctionality not directly related to the invention is not described,e.g. removing the NGAP context between BS1 and core NW AMF when the UEcontext is fetched to the new BS2 (gNB). In addition, the current 5Gnode names and message names are examples, and are used but those arenot binding in the sense that the essence of the invention can be usedfor other (radio) access technologies and with other similar messages.

Although various aspects are set out above, other aspects comprise othercombinations of features from the described embodiments, and not solelythe combinations described above. If desired, the different functionsdiscussed herein may be performed in a different order and/orconcurrently with each other. Furthermore, if desired, one or more ofthe above-described functions may be optional or may be combined.

Although various aspects of the invention are set out in the independentclaims, other aspects of the invention comprise other combinations offeatures from the described embodiments and/or the dependent claims withthe features of the independent claims, and not solely the combinationsexplicitly set out in the claims.

It is also noted herein that while the above describes examples ofembodiments of the invention, these descriptions should not be viewed ina limiting sense. Rather, there are several variations and modificationswhich may be made without departing from the scope of the presentinvention as defined in the appended claims.

The invention claimed is:
 1. An apparatus comprising: at least oneprocessor; and at least one memory including computer program code,wherein the at least one memory and the computer code are configured,with the at least one processor, to cause the apparatus to at least:receive a radio resource control (RRC) message from a user equipment,wherein the RRC message is sent by the user equipment when resuming froman RRC inactive state to an RRC connected state, the RRC messagecombining a radio access network notification area (RNA) update with acore network level non-access stratum (NAS) registration procedure; andsend an RRC response message to the user equipment.
 2. The apparatus ofclaim 1, wherein the RRC message comprises a cause value indicating acombined RNA update with an NAS message.
 3. The apparatus of claim 1,wherein the RRC message comprises an RRC resume request and the RRCresponse message comprises an RRC resume or RRC release.
 4. Theapparatus of claim 1, wherein the RRC message further comprises an NASmessage.
 5. The apparatus of claim 4, wherein the NAS message comprisesan NAS registration request.
 6. The apparatus of claim 1, wherein theRRC response message further comprises an NAS response.
 7. The apparatusof claim 6, wherein the NAS response comprises NAS registration accept.8. The apparatus of claim 1, wherein the apparatus is further caused toperform at least one of: send an NAS message to a network node; receivean NAS response from the network node.
 9. The apparatus of claim 1,wherein the apparatus is further caused to: determine, in response toreceiving an NAS response from a network node, whether to resume orrelease RRC connection; and send an RRC resume or RRC release to theuser equipment based on the determination, or send an RRC downlinkinformation transfer or RRC release to the user equipment based on thedetermination.
 10. The apparatus of claim 1, wherein the RRC responsemessage comprises an RRC resume complete and the RRC resume completecomprises an NAS message.
 11. The apparatus of claim 1, wherein the RRCmessage is received in response to at least one of the events: a changeof base station, an RNA update, a periodic RNA update, a registrationupdate and a periodic registration update.
 12. An apparatus comprising:at least one processor; and at least one memory including computerprogram code, wherein the at least one memory and the computer code areconfigured, with the at least one processor, to cause the apparatus toat least: send a radio resource control (RRC) message, wherein the RRCmessage is sent by the apparatus when resuming from an RRC inactivestate to an RRC connected state, the RRC message combining a radioaccess network notification area (RNA) update with a core network levelnon-access stratum (NAS) registration procedure; and receive an RRCresponse message.
 13. The apparatus of claim 12, wherein the RRC messagecomprises a cause value indicating a combined RNA update with an NASmessage.
 14. The apparatus of claim 12, wherein the RRC messagecomprises an RRC resume request and the RRC response message comprisesan RRC resume or RRC release.
 15. The apparatus of claim 12, wherein theRRC message further comprises an NAS message.
 16. The apparatus of claim15, wherein the NAS message comprises an NAS registration request. 17.The apparatus of claim 12, wherein the RRC response message furthercomprises an NAS response.
 18. The apparatus of claim 17, wherein theNAS response comprises NAS registration accept.
 19. The apparatus ofclaim 12, wherein the RRC response message comprises an RRC resumecomplete and the RRC resume complete comprises an NAS message.
 20. Theapparatus of claim 12, wherein the RRC response message comprises an RRCdownlink information transfer or RRC release, and wherein the RRCdownlink information transfer or the RRC release comprises an NASmessage.
 21. The apparatus of claim 12, wherein the RRC message is sentin response to at least one of the events: a change of base station, anRNA update, a periodic RNA update, a registration update and a periodicregistration update.
 22. A method comprising: sending, by a userequipment, a radio resource control (RRC) message, wherein the RRCmessage is sent by the user equipment when resuming from an RRC inactivestate to an RRC connected state, the RRC message combining a radioaccess network notification area (RNA) update with a core network levelnon-access stratum (NAS) registration procedure; and receiving, by theuser equipment, an RRC response message.